This invention relates generally to apparatus and methods of using the apparatus for drilling lateral or multi-lateral wells from a vertical well, for the purpose of producing more oil and gas from the subsurface formations and for entry and reentry into said multi-lateral wells after hey have been completed. Specifically this invention relates to novel and improved assemblies and methods for the installation and completion of lateral well bores emanating from a main casing or a tubular walled member which may be vertical, deviated or horizontal and their entry or reentry.
Since the increase in usage of lateral or multi-lateral well drilling, there has also been an increase in the problems associated with their drilling because they are being used in more and different well conditions and at more extreme angles of deviation from the vertical well bore than ever before. Thus many techniques have been developed to solve some of these problems but only with the result of creating other and different problems, not the least of which is providing a simple and universal assembly and method which can be used for both drilling and completion and also entry and reentry at a later date.
The prior art is replete with keys formed, as for example in U.S. Pat. No. 4,415,205, on the inside of the well bore and casing and which project inwardly to locate and orient the whip stock and other tools for drilling a lateral well. These internally projecting keys which function by extending radially inward from the casing wall from for orienting and positioning a whipstock, restrict the internal clearance through the casing. This is a problem because it limits the operating diameter of the well bore which restricts the ability to operate other tools in the well when needed. Further because of the large forces used in wells with the pipe and tools being moved up and down, these internal projections are subject to being damaged or destroyed by tools working in the casing, which would render the projections useless for their intended purpose. Thus the expense of a window section would be completely lost, as well as access to that oil bearing strata without great expense. This is especially true in the case of reentry at some later time after the well has been in service for some time and some workover operation is needed to be performed.
Also as the multi-lateral drilling assemblies have become longer and more complex these assemblies and their methods have become more likely to have problems associated with retrieveing and manipulating them in the well bores.
A yet further problem is finding the exact location of the window junction in the well bore after it has been properly oriented. The prior art, such as in U.S. Pat. No. 5,579,829, has used spring loaded keys, for locating and orienting operations related to the geological formulations for these lateral well bores. However many of these keys were equipped with multiple sets of keys which must mate with permanenly mounted key-receivers located in the main casing. This could be a relatively complex arraignment and procedure and it required diligence and accuracly in placing the correct combinations of keys in the system accurately. Also it required a very detailed and complicated record keeping procedure for any future work which might be done in the well for the future. Also as the various key-receives for each well could be different it required the maintenance of a large inventory of each key system and this problem is growing as the number of such systems is increasing around the world.
Also in these spring loaded key systems the keys while easy to engage once the key was directly over the key hole or key way, these key holes and ways were of relatively small square area and a significant amount of time could be required for fishing around to find the exact position to allow the key to spring out and mate with the key holes and key ways. In most cases the keys had to hit key holes and ways with target areas measured in 25 to 50 square inches.
Also in the prior art many times these small target areas could become filled with debris from the well fluids and then the spring loaded key would not have a space into which it could engage, with the corresponding problems of not being able to set the whip stock or other tools without additional work and runs back into the hole to clear the key hole or key ways.
Also in the prior art these premilled windows had to be covered with a metal sleeve which in some cases were pulled from the hole and this increased the costs of well operation, as those skilled in the art will appreciate, every trip into the hole adds costs to a well operation. Some of the other prior art patents attempted to solve this problem by putting metal covers permanently fixed to the premilled windows which were then required to be milled out after the well casing was cemented and set in place. The problem with this approach is that many metal cuttings were dropped and dumped into the well which has the potential for creating problems with other well operating equipment and the circulation of mud and other equipment which is hydraulically driven by the well fluids.
Yet another problem in the prior art is the reentry of the at least one multi-lateral well once it has been drilled and completed, because in most cases the whip stock and other orientating devices have been removed from the well and the entry way to the multi-lateral well has few if any means of identifying the entrance to the at least one multi-lateral well bore.
Also a problem, which those skilled in the are will appreciate, is the problem of being able to move from a vertical position in a casing or tubular wall to a kicked out position from the vertical position in a casing or tube, which must occur, to achieve reentry into at least one of the multi-lateral well bores. While there have been many ways in the prior of achieving such a kick out position such as resetting a whip stock, etc., all of these ways and tools required multiple entries back into the well to first set the orientation piece and then to run the tool which was going to actually reenter the at least one multi-lateral well with the added costs associated with multiple re-runs back into a well.
A further problem was even finding the proemilled window because if the well is an older one many of the keys or indicators which were originally attached or fixed in the casing or tubular walls have been damaged or destroyed by other work that has occurred in the well since the drilling of the at least one multi-lateral well.
Also in the prior art the ability to reenter a well is many times totally dependant on the accuracy of the historical records kept on a well and the older the well the less likely the well records were likely to be available for use in the reentry process which rendered reentry either impossible of very expensive.